PDCD1 and Merkel cell skin cancer: When compared to previous chemotherapeutic modalities, management of advanced MCC has significantly been improved since the introduction of immune checkpoint inhibitors (ICI) such as anti-programmed cell death protein 1 (PD-1) inhibitors (pembrolizumab, nivolumab) and anti-programmed cell death ligand protein 1 (PD-L1) inhibitors (avelumab) [6,7,8].